Beneficiating agents

ABSTRACT

The present invention relates to compositions of matter which are especially useful as beneficiating agents in the production of well drilling muds. These compositions comprise mixtures of carboxylic acid polymers and metal salts which mixtures are water soluble at a pH of less than 7.0 wherein the metal is selected from groups IB, IIB, VIB, VIIB and VIII of the Periodic Table and lead.

United States Patent [191 Le Blane BENEFICIATING AGENTS [75] Inventor:John R. Le Blane, Wilbraham, Mass. [73] Assignee: Monsanto Company, St.Louis, Mo. [22] Filed: May 5, 1972 [21] Appl. No.: 250,619

7 [52] US. Cl. 252/8.5 A, 210/51, 252/8.5 C,

252/8.55 R, 252/316, 260/29.6 S, 260/29.6 H,

" 260/29.6 M, 260/41 A, 260/41 R [51] Int. Cl Cl0m 3/22 [58] Field ofSearch 252/8.5 A, 8.5 C, 8.55 R, 252/316; 210/51, 54; 260/41 A [56]References Cited UNITED STATES PATENTS 2,605,221 7/1952 Hoeppel 252/8.52,702,788 2/1955 Dawson 252/8.5 2,948,678 8/1960 Turner et a1... 252/8.53,081,260 3/1963 Park .1 252/8.5

[451 June 11, 1974 3,220,946 11/1965 Turner ..252/8.5 3,558,545 1/1971Lummus ..252/8.5

FOREIGN PATENTS OR APPLICATIONS 725,460 3/1955 Great Britain PrimaryExaminerHerbert B. Guynn Attorney, Agent, or FirmR. Bruce Blance; EdwardP. Grattan; James C. Logomasini 5 7 ABSTRACT 15 Claims, N0 Drawings IBENEFICIATING AGENTS BACKGROUND OF THE INVENTION 1. Field of theInvention The present invention relates to compositions of matter whichare useful as beneficiating agents for clays used in the production ofwell drilling muds.

2. Description of the Prior Art Clay beneficiating agents for welldrilling muds are commonly used in the industry in order to improve theyield of the mud. These beneficiating agents and drilling muds aredescribed at length in such references as U.S. Pat. Nos. 2,948,678,3,070,543, 3,,070,544, and 3,558,545, as well as in other references. Inspite of the improved yields obtained with the beneficiating agentsdescribed in the above references a need exists in the art for moreefficient beneficiating agents which will give increased yields.

SUMMARY OF THE INVENTION In accordance with the present invention acomposition of matter is provided which improves the yield of a clayused in drilling muds. The composition of matter is a mixture of atleast one carboxylic acid polymer and at least one metal salt whichmixture has a water solubility of at least 1 percent by weight at a pHless than 7.0 wherein the metal is selected from the group consisting oflead and a metal from Groups IB, IIB, VIB, VIIB and VIII of the PeriodicTable as set forth at pages 56 and 57 of LANGES HANDBOOK OF CHEMIS- TRY,Ninth Edition, McGraw-Hill Book Company, New York (1956).

DESCRIPTION OF THE PREFERRED EMBODIMENTS The carboxylic acid polymercomponent of the beneficiating agents of the present invention ischaracterized by being water soluble at a pH less than 7 and morepreferably in the pH range of from 2.0 to 6.5. The amount of solubilityshould be such that the polymer will form at least a 1 percent solutionin water at 25 C. at a pH in the above specified ranges.

The preferred polymers are further characterized by having a numberaverage molecular weight of at least 5,000. There is no upper limit onthe molecular weight except that the practical limit is determined bythe water solubility of the polymer. Those skilled in the art realizethat higher molecular weight polymers will provide a higher solutionviscosity and more beneficiating ability at a given polymerconcentration. However, there is a practical upper limit on themolecular weight in the terms of the water solubility of the polymer andeventually a point will be reached with increasing molecular weightwhere the polymer no longer meets the solubility requirements outlinedabove.

The amount of carboxylic acid groups in the polymer is in the range offrom 20 mol percent to 100 mol percent and more preferably 40 molpercent to 100 mol percent based on the total polymeric composition.These polymers are the homopolymerization products of carboxylic acidmonomers such as acrylic acid, methacrylic acid, etc. Alternately, thepolymers are interpolymerization products of at least one carboxylicacid monomer and at least one other monomer which is copolymerizabletherewith. Examples of the carboxylic acid monomer used in theinterpolymers include acrylic acid, methacrylic acid, maleic anhydride,maleic acid, fumaric acid, crotonic acid and itaconic acid, mesaconicacid, citraconic acid, etc. Examples of monomers which arecopolymerizable with the carboxylic acid monomer include lower alphaolefins containing from 2 to 4 carbon atoms such as ethylene, propylene,butylene, isobutylene, alkyl vinyl ethers wherein the alkyl groupcontains 1 to 4 carbon atoms such as vinyl methyl ether, vinyl ethylether, vinyl propyl ether, vinyl butyl ether, vinyl isobutyl ether;vinyl esters such as vinyl formate, vinyl acetate, vinyl propionate,vinyl butyrate and vinyl benzoate; esters of acrylic and methacrylicacid wherein the alcohol moiety of the ester contains from 1 to 8 carbonatoms such as methyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate,methyl methacrylate, ethyl methacrylate, 2-ethylhexyl methacrylate;vinyl aromatic monomers such as styrene, alphamethyl styrene,chlorostyrene, vinyl toluene, etc.; amide type monomers such asacrylamide, methacrylamide, alkylol acrylamides such as methylolacrylamide, ethylol acrylamide, methylol methacrylamide, ethylolmethacrylamide, methylol ethacrylamide,

ethylol ethacrylamide, etc.; N-methylolated acrylamides and theN-methylolated methacrylamides which are etherified with a lower alkanolsuch as methanol, ethanol, propanol and butanol, etc. Care must be takenin the choice of comonomer and the amount thereof so that the aboverequirement of water solubility is met.

Preferred polymers for use in the present invention are poly(vinylacetate-maleic anhydride), poly(ethylene-maleic anhydride), poly( vinylmethyl ether-maleic anhydride) and polyacrylic acid.

The metal salt component of the beneficiating agents of the presentinvention is selected from water soluble organic and inorganic metalsalts of lead and metals of Groups IB, IIB, VIB, VIIB and VIII of thePeriodic Table. The solubility is such that the salt will form at leasta 1 percent solution in water at 25 C. at a pH less than 7.0. Theseinclude water soluble inorganic sulfates, nitrates and chlorides as wellas metal salts of aliphatic monocarboxylic acids such as formic, acetic,propionic, n-butyric, isobutyric, etc. Preferred are organic acid saltsof aliphatic monocarboxylic organic acids containing from 1 to 4 carbonatoms, where the metal is selected from the group consisting of zinc,chromium, nickel, manganese, cobalt and lead. Especially preferred arethe formates and acetates of zinc, chromium, nickel. manganese, cobaltand lead.

The amount of water-soluble metal salt used in the beneficiating agentsof the present invention is in the range of from 5 to percent by weightbased on the total weight of polymerand metal. More preferably, theamount of salt is in the range of from 5 to 70 percent by weight.Conversely, the amount of polymer in the beneficiating agent is in therange of from to 20 percent and more preferably 95 to 30 percent byweight.

The amount of beneficiating agents (polymer and salt) used in thepresent invention depends to some ex tent on the degree of beneficiationdesired and varies with the clay. Generally, only very small quantitiesare required and amounts within the range from about 0.1 to about 10 lb.per ton of clay will produce satisfactory results. The preferredquantities for treatment are from about 1.5 to 3.5 lb. of beneficiatingagent per ton of clay. In general, the yield obtainable at aconcentration of 3 lbs. of the interpolymers per ton of clay lies in therange from 160-190 barrels. With some clays, yields as high as 270barrels have been achieved by increasing the concentration to 3.5lb./ton of clay. In some instances, a maximum yield of 150 barrels isobtained with 1.5 lb. of the interpolymers per ton of clay and furtheraddition results in a decrease in yield value.

The beneficiating agents of the present invention are prepared by dryblending the polymeric and metal salt components, by mixing aqueoussolutions of these components or by dissolving one component in asolution of the other component. Alternately, the polymeric and metalsalt components may be dry blended with the clay or added to clayslurries which may already contain the other component. Other methodswell known to those skilled in the art may also be used.

A preferred embodiment of the present invention calls for the use of aflocculating agent in combination with the clay beneficiating agents ofthe present invention. The flocculating agents are used in amounts offrom to 100 percent by weight based on the weight of the polymericcomponent of the beneficiating agent. Examples of these flocculatingagents, which are well known in the art, include polyacrylamide, starchand starch derivatives, polyethylene oxide, polyacrylic acid, etc.

The clays which are used in well drilling operations are well known tothose skilled in the art. Especially preferred are the montmorilloniteand bentonite clays. Species of these clays include beidellite,nontronite, hectorite and saponite. Some of these clays are presentlytoo expensive for use in drilling muds, but nevertheless are susceptibleto having their yield increased by the practice of this invention. As apractical matter, the invention will find its widest application inconjunction with the beneficiation of bentonite or montmorillonite.These clays, in the raw state, usually have a rather low yield of theorder of 30 to 35 barrels per ton and will desirably be beneficiateduntil the yield exceeds 90 barrels per ton so as to meet the minimumspecifications of many purchasers.

The beneficiating agents of the present invention can be added to theclay in any desired manner. In general, a simple mechanical mixture ofthe clay and beneficiating agent is prepared by dry-blending thebeneficiating agent in powder form directly with dry clay. This can bedone conveniently at the time the clay is ground in a roller mill, forexample. Alternatively, an aqueous solution of the beneficiating agentmay be sprayed directly onto the clay either in stock piles, aftercrushing, during the grinding operation, or during a bag-packingoperation. Also, if desired, the clay and beneficiating agent can beseparately added in any desired order to form a slurry. This type of wetmixing could be employed, for example, at the well site.

The yield of a clay such as bentonite is expressed as the number ofbarrels of centipoises mud which can be prepared from one ton of clay.The effectiveness of polymers in increasing yield is determined byadding 0.05 pound of the polymer per barrel of bentonite dispersions andthen determining the yield. Solutions of one percent by weight of thepolymers are used to insure adequate mixing of the polymer in the mudand to avoid the weighing of the small quantities of polymer required.The concentration of betonite used is 2.8 and 4 percent by weight, or 10and 14 pounds per barrel.

The bentonite is added to 350 milliliters of water in a quart jar. It isthen mixed on a Hamilton Beach Mixer, Model 30, at approximately 12,000rpm. for a total of 20 minutes. After 10 minutes of mixing, anybentonite which is on the sides of the jar is scraped back and mixing iscontinued for 5 minutes. The polymer is then added, generally 5 cc. of aone percent solution (0.05 pound per barrel) and the mud is mixed forthe remaining 5 minutes. The properties are measured immediately aftermixing, a Fann viscometer being used, and the fluid loss is alsodetermined. To calculate the yield the logarithm of the apparentviscosity l/2 of the 600 rpm. Fann reading) is plotted against the clayconcentration in pounds per barrel. From the plotted data, the clayconcentration required to give a viscosity of 15 cps. is determined. Theyield in barrels per ton is calculated by the following equation:

Where:

Y yield in barrels per ton.

c clay concentration in pounds per barrel.

The basic method used to evaluate polymers for flocculation of low-yieldclay is as follows: 4.0 grams of clay are added to approximatelymilliliters of water in a stoppered l00-milliliter graduated cylinder.The clay-water mixture is thoroughly mixed by shaking, then is made upto 99 milliliters with water. 1.0 Milliliter of the polymer solution (1percent by weight) is added and the mixture agitated for one minute byinverting the cylinder. The cylinder is then placed in an uprightposition and the timer started. The height (in milliliters) of theinterface between the clear water and the flocculated settling solids isread and recorded at the following time intervals, 10 seconds, 30seconds, 50 seconds, 80 seconds, 100 seconds, seconds, 200 seconds, and400 seconds. The logarithm of the time is plotted against the height oftheinterface. From the curve drawn, the time to obtain 50 milliliters ofsettling is determined and reported. The height of the solids after 10seconds, will give somewhat of a measure of the time for the flocs toform and the 400-second reading will indicate the floc size.

Several methods can be used to prepare the improved drilling muds of thepresent invention. The beneficiating agent or the components thereof canbe sprinkled dry over the mud pit. The beneficiating agent or componentsthereof can also be added through a hopper to the flowing mud stream. Itis very much preferred, however, to prepare an aqueous solution of thebeneficiating agent in a concentration of about 1 percent by weight.This solution is then added intermittently, or preferably continuously,to the mud system. The point of addition is usually at the point wherethe mud enters the well or leaves the mud pit. In some cases,introduction at other points, or at multiple points is advisable.

The following examples are set forth in illustration of the presentinvention and should not be construed as a limitation thereof. All partsand percentages given are by weight unless otherwise indicated.

EXAMPLE 1 (CONTROL) This example is set forth to illustrate thebeneficiating agents of the prior art. The beneficiating agent used inthis example is as follows:

poly(vinyl acetate-maleic anhydride) (1) 55 parts polyacrylamide (2) 10parts soda ash (sodium carbonate) 28 parts calcium hydroxide 7 parts (1)1:! mol ratio having a specific viscosity of about 4.0 as measured as a1 percent solution in cyclohexanonc at 25 C., which is commericallyavailable as Lytron 887 from Monsanto Company.

(2) Flocculating agent commcrically available as Separan NP-l() from DowChemical Company.

Yield tests as described above, are carried out using the foregoingbeneficiating agent in combination with five different grades ofbentonite clay which are arbitrarily designated A to E. The results ofthese tests are listed in Table 1 below along with the results of aflocculation test.

EXAMPLE 2 poly(vinyl acetate-maleic anhydride) 55 parts polyacrylamide lparts zinc acetate 35 parts Yield tests are carried out as above and theresults are reported in Table 1 below along with the results of aflocculation test.

TABLE I SUMMARY OF YIELD TESTS FOR EXAMPLES l and 2 Type of BentoniteYield Tests (Barrels of mud) Used Example 1 Example 2 A 150 232 B I I4I76 C 130 184 D 126 177 E I36 189 FLOCCULATION TESTS ExampleFlocculation Time (Seconds) EXAMPLE 3 Examples 1 and 2 are repeated hereusing the bentonite clay designated as A, except that the polyacrylamideflocculating agent is omitted from the formulations. The purpose of thisexample is to illustrate that the beneficiating agents of the presentinvention improve the yield of mud regardless of whether or not aflocculating agent is used. The results of these tests are set forthbelow:

As is evident from the above data the beneficiating agents of thepresent invention provide a significant improvement in yieldindependently of the use of a flocculating agent.

EXAMPLE 4 Example 2 (using the bentonite designated as A) is repeatedhere except that other water soluble metal salts are used in place ofthe zinc acetate used in Example 2. Results of the yield andflocculation tests are set forth below:

Flocculation Periodic Table Time Metal Salt Group Yield (Seconds)Example 1 (Control) lA, "A I4 Manganese formate VllB Nickel acetate Vlll186 15 Chromium acetate VlB I60 14 Cupric acetate [8 250 20 Cobaltousacetate Vlll ISI 16 Lead Acetate lVB l8! test not run EXAMPLE 5 Thisexample illustrates the use of a water-soluble ethylene-maleic anhydridecopolymer as the polymeric component in the beneficiating agents of thepresent invention. The poly(ethylene-maleic anhydride) used ischaracterized as having a carboxylic acid content of about 50 molpercent and a specific viscosity of about 2.0 as measured as a 1 percentsolution in cyclohexanone at 25 C. The bentonite designated as A inExample 1 and 2 above, is used in this example. Three tests are carriedout using the polymer alone, the polymer with the metal salts of theprior art (Example 1 and the polymer with the zinc acetate of Example 2in accordance with the practice of the present invention. The samerelative amounts of polymer and metal salts used in Examples 1 and 2 areused here.

The results of the yield tests are set forth below:

Beneficiating Agent Yield EMA Alone (1) 100 EMA soda ash calciumhydroxide 100 EMA zinc acetate [70 (l) EMA poly(cthylene-maleicanhydride) EXAMPLE 6 EXAMPLE 7 Example 3 is repeated here except using awater solu ble polyacrylic acid and zinc acetate. The yield value ofthis system is 269.

EXAMPLES 8-9 These examples are set forth to illustrate some of thevariations in the amounts of polymer and metal salt which can be used inthe practice of the present invention. No flocculating aid is used inthese examples and the polymer and metal salt used are the same as thoseused in Example 2.

Example Amount of Polymer Amount of Metal Salt Yield 8 35 parts 65 parts'2l7 9 95 parts parts l66 EXAMPLE 10 This example illustrates the needfor using a poly- One advantage of the compositions of the presentinvention is that they can be used with poor grades of bentonite toincrease the effectiveness of such material to a point comparable tothat expected for good grades of bentonite. This can be particularlyimportant in relatively inaccessible areas having readily available poorgrades of bentonite, but no high-quality clays.

By use of these compositions, the viscosity of water containing a verylow concentration of bentonite can be increased and the fluid loss canbe decreased to increase the efficiency of the water when used as afracturing fluid. Due to the low concentration of bentonite, there isless tendency for the fracture to become plugged by the clay when thewell is put back on production. The same advantage applies to diluteclay slurries used opposite zones to be perforated with bullet or jetperforators.

In addition to being used as beneficiating agents for drilling muds, thecompositions of the present invention may also be used as binders forceramic materials, thickening agents, coagulants, textile sizes, cementadditives, etc.

What is claimed is:

1. An aqueous drilling mud comprising water, clay of bentonite ormontmorillonite type and a mixture of (A) from 95 to percent by weightofa polymer of at least one carboxylic acid monomer selected from thegroup consisting of acrylic acid, methacrylic acid, maleic anhydride,maleic acid, fumaric acid, crotonic acid, itaconic acid, mesaconic acid,and citraconic acid, and (B) from 5 to 80 percent by weight of at leastone water soluble sulfate, nitrate, chloride or aliphatic monocarboxylicacid salt of a metal selected from the group consisting of lead and ametal of Groups 18, [IB, VIB, VllB and VIII of the Periodic Table;wherein the carboxylic acid polymer is characterized as having acarboxylic acid monomer content in the range of from 20 to 100 molpercent, a number average molecular weight of at least 5,000, and asolubility in water at a pH of less than 7 of at least 1 percent byweight at 25 C.; wherein the salt has a water solubility of at least 1%by weight at a pH less than 7, wherein the mixture has a watersolubility of at least 1 percent by weight at a pH less than 7 andwherein the amount of the mixture of carboxylic acid polymer and saltused is in the range of from about 0.1 to about 10 pounds per ton ofclay.

2. The drilling mud as in claim 1 wherein the soluble metal salt is ametal salt of an aliphatic monocarboxylic acid containing from 1 to 4carbon atoms.

3. The drilling mud as in claim 1 wherein the soluble metal salt isselected from the group consisting of acetates and formates ofmanganese, nickel, chromium, copper, cobalt and lead.

4-. The drilling mud as in claim 1 wherein the polymer is polyacrylicacid.

5. The drilling mud as in claim 1 wherein the polymer is a copolymer ofvinyl acetate and maleic anhydride.

6. The drilling mud as in claim 1 wherein the polymer is a copolymer ofethylene and maleic anhydride.

7. The drilling mud as in claim 1 wherein the polymer is a copolymer ofvinyl methyl ether and maleic anhydride.

8. The drilling mud as in claim 1 wherein the amount of water solublepolymer in the mixture is in the range of from 95 to 30 percent byweight and the amount of soluble metal salt is in the range of from 5 topercent by weight.

9. The drilling mud as in claim 1 wherein the metal salt is zincacetate.

10. The drilling mud as in claim 1 which further includes apolyacrylamide flocculating agent.

11. An aqueous drilling mud comprising water, a bentonite clay and amixture of (A) from to 20 percent by weight of a polymer of at least onecarboxylic acid monomer wherein the polymer is selected from the groupconsisting of polyacrylic acid, poly(vinyl acetate-maleic anhydride),poly(ethylene-maleic anhydride), and poly(vinyl methyl ether-maleicanhydride); and (B) from 5 to 80 percent by weight of at least one watersoluble sulfate, nitrate, chloride or aliphatic monocarboxylic acidmetal salt of an aliphatic carboxylic acid containing from 1 to 4 carbonatoms and a metal selected from the group consisting of lead and a metalof Groups IB, IlB VlB, V118 and VIII of the Periodic Table; wherein thecarboxylic acid polymer is characterized as having a carboxylic acidmonomer content in the range of from 20 to mol percent, a number averagemolecular weight of at least 5,000, and a solubility in water at a pH ofless than 7 of at least 1 percent by weight at 25 C.; wherein the salthas a water solubility of at least 1 percent by weight at a pH less than7, wherein the mixture has a water solubility of at least 1 percent byweight at a pH less than 7 and wherein the amount of the mixture ofcarboxylic acid polymer and salt in the drilling mud is in the range offrom about 1.5 to about 3.5 pounds per ton of clay.

E2. The drilling mud as in claim 11 wherein the solu ble metal salt isselected from the group consisting of acetates and formates ofmanganese, zinc, nickel, chromium, copper, cobalt and lead.

13. The drilling mud as in claim 11 wherein the salt is zinc acetate.amount of water soluble polymer in the mixture is in 15. The drillingmud as in claim 11 which further inthe range of from 95 to 30 percent byweight. cludes a polyacrylamide flocculating agent.

14. The drilling mud as in claim 11 wherein the metal

2. The drilling mud as in claim 1 wherein the soluble metal salt is ametal salt of an aliphatic monocarboxylic acid containing from 1 to 4carbon atoms.
 3. The drilling mud as in claim 1 wherein the solublemetal salt is selected from the group consisting of acetates andformates of manganese, nickel, chromium, copper, cobalt and lead.
 4. Thedrilling mud as in claim 1 wherein the polymer is polyacrylic acid. 5.The drilling mud as in claim 1 wherein the polymer is a copolymer ofvinyl acetate and maleic anhydride.
 6. The drilling mud as in claim 1wherein the polymer is a copolymer of ethylene and maleic anhydride. 7.The drilling mud as in claim 1 wherein the polymer is a copolymer ofvinyl methyl ether and maleic anhydride.
 8. The drilling mud as in claim1 wherein the amount of water soluble polymer in the mixture is in therange of from 95 to 30 percent by weight and the amount of soluble metalsalt is in the range of from 5 to 70 percent by weight.
 9. The drillingmud as in claim 1 wherein the metal salt is zinc acetate.
 10. Thedrilling mud as in claim 1 which further includes a polyacrylamideflocculating agent.
 11. An aqueous drilling mud comprising water, abentonite clay and a mixture of (A) from 95 to 20 percent by weight of apolymer of at least one carboxylic acid monomer wherein the polymer isselected from the group consisting of polyacrylic acid, poly(vinylacetate-maleic anhydride), poly(ethylene-maleic anhydride), andpoly(vinyl methyl ether-maleic anhydride); and (B) from 5 to 80 percentby weight of at least one water soluble sulfate, nitrate, chloride oraliphatic monocarboxylic acid metal salt of an aliphatic carboxylic acidcontaining from 1 to 4 carbon atoms and a metal selected from the groupconsisting of lead and a metal of Groups IB, IIB VIB, VIIB and VIII ofthe Periodic Table; wherein the carboxylic acid polymer is characterizedas having a carboxylic acid monomer content in the range of from 20 to100 mol percent, a number average molecular weight of at least 5,000,and a solubility in water at a pH of less than 7 of at least 1 percentby weight at 25* C.; wherein the salt has a water solubility of at least1 percent by weight at a pH less than 7, wherein the mixture has a watersolubility of at least 1 percent by weight at a pH less than 7 andwherein the amount of the mixture of carboxylic acid polymer and salt inthe drilling mud is in the range of from about 1.5 to about 3.5 poundsper ton of clay.
 12. The drilling mud as in claim 11 wherein the solublemetal salt is selected from the group consisting of acetates andformates of manganese, zinc, nickel, chromium, copper, cobalt and lead.13. The drilling mud as in claim 11 wherein the amount of water solublepolymer in the mixture is in the range of from 95 to 30 percent byweight.
 14. The drilling mud as in claim 11 wherein the metal salt iszinc acetate.
 15. The drilling mud as in claim 11 which further includesa polyacrylamide flocculating agent.